Reconstruction of Heel Soft Tissue Defects: An Algorithm Based on Our Experience

BACKGROUND Sensory recovery and durability of the flap is the primary goal of heel soft tissue reconstruction. From the different options, the choice of the flap depends on the size of the defect, its location, and the availability of the donor area. METHODS In this retrospective study, 40 patients having heel defects were included from Jan 2016 to Dec 2018 in which different flaps were used for the reconstruction. The outcome was evaluated in terms of flap survival, recovery of sensation, the durability of coverage, and functional denouement. We also analysed the outcome between neuropathic and non-neuropathic ulcers of the heel. RESULTS Out of 40 patients’ medial plantar artery islanded flap was performed in eight cases, extended reverse sural flap in 16 cases, islanded reverse sural flap in six cases, local flaps in six cases, cross-leg flap in two cases, and free Latissimus Dorsi muscle flaps with Skin Graft cover in two cases. The patients were observed for a mean follow-up time of 15 months (12-20 months). Only two flaps showed marginal necrosis as an immediate complication. The majority of the flaps were tenacious in the follow-up period except for the six flaps that developed delayed ulceration. Return of protective sensation (P=0.006) and mean American Orthopaedic Foot and Ankle Society subjective score (P=0.025) was significantly higher in the non-neuropathic ulcer group. CONCLUSION Locoregional flaps can cover most of the heel defects with a satisfactory outcome. The functional outcome was lower in the reconstructed neuropathic heel ulcer group.


INTRODUCTION
Reconstruction of the heel soft-tissue defect with sensate and durable tissue which can offer a productive life to the patient is still challenging. As the heel is a weight-bearing part of the body and subject to repetitive trauma, heel defects are quite common in the working Indian population. The heel is a specialized tissue in the body having a thick epidermis and dermis, firmly anchored to the plantar aponeurosis by perpendicular fibrous Septa which prevents shearing force and fat loculi present between these vertically orientated septa provide a shock-absorbing function [1][2][3] . Defects in this region can occur due to trauma, burns, tumor excision, or trophic ulcer. In the case of superadded infections, it may potentially lead to secondary amputation 4,5 . Trauma in the form of avulsion injury of the heel can lead to loss of total or isolated posterior heel, associated with exposed Achilles tendon, or calcaneal bone fracture [6][7][8] . On the other hand, Tumor, and Neurogenic ulcers commonly involve anterior weight wearing part of the heel. Neurogenic ulcers develop in patients with neuropathies like Hansen's disease, diabetic neuropathies, syringomyelia, spina bifida, traumatic nerve injuries, etc. Because there is a loss of protective sensation in these patients and they do not relieve pressure intermittently over pressure points, it leads to skin breakdown and ulceration due to repetitive trauma 9 . Reconstruction of the heel with similar tissue is challenging because of the limited availability of glabrous local tissue. Different options for reconstruction of the heel are skin graft, locoregional flaps, cross-leg flap and different free flaps with each of them has their pros and cons 10 . This single-center study was conducted to evaluate the various flap options available to cover heel defects. We also entailed flap survivability, sensory recovery along with a comparison of functional outcomes between neuropathic and non-neuropathic heel ulcer groups.

MATERIALS AND METHODS
In this retrospective study, an analysis was performed using the medical records of 40 patients undergone soft tissue reconstruction of the heel at All India Institute of Medical Science, Bhopal, India from Jan 2016 to Dec 2018. The study was approved by the Institutional Review Board (Ethics code: IHEC-LOP/2020/IM0259) and informed consent has been obtained from all participants prior to enrolment. Patient's data including age, sex, concomitant medical illness, etiology, defect size, and the location was recorded. Wounds were prepared by debridement, daily dressing, and antibiotic coverage according to the wound swab culture report. The soft tissue defects of the heel were classified as anterior when located on the weight-bearing part of the heel, posterior when they were located on the nonweight-bearing part of the heel, and complete when involving the anterior as well as the posterior heel 7,11 . Based on the location of the heel defect, its size, and available options, various flaps were planned ( Figure  1). Local V-Y advancement and rotation flaps were utilized to cover small defects at the anterior heel region. Advancement of avulsed heel flaps was used to cover small defects at the posterior heel region. (Figure 2A). Medial Plantar Artery islanded (MPA) flaps were harvested to cover moderate size defects at the anterior heel region ( Figure 3A). Preoperatively Handheld Doppler was used to confirming the presence of the Medial Plantar artery. The MPA islanded flap was first described by Harrison and Morgan 12 in which the distal end of the medial plantar artery was divided and elevated with the flap. Here all the Medial Plantar Artery flaps were raised based on the superficial subcutaneous branch of the medial plantar artery in spinal block anaesthesia under tourniquet control and loop magnification 13 . This approach prevents the sacrifice of the medial plantar artery and maintains its continuity. Cutaneous nerve included in flaps where the sensation of the sole was intact. After completion of flap dissection, an incision was made over intact skin between the donor and recipient area for the flap transposition, sutured after the flap inset. The donor site was covered by a split-thickness skin graft. Postoperative immobilization of the ankle joint was done with a dorsal splint till skin graft take-up. Extended reverse sural artery (RSA) flaps were performed to cover complete heel defects ( Figure  4A) as well as to cover defects at the anterior heel when the Medial plantar artery flap was not feasible ( Figure 3B). Posterior heel defects without avulsion www.wjps.ir     (Table 1) 10.15,16 . The sensation was objectively assessed by using the Semmes-Weinstein monofilament test at the flap site, with 3 different monofilament sizes (size 6.65=300 g for deep sensation, size 4.31=2 g for protective sensation, and size 3.61=0.4 g for normal touch sensation) 10,17 . Soft tissue breakdown was noted clinically to assess the durability of the flap.

Statistical analysis
The data were entered in an MS Excel spreadsheet and analysis was done using SPSS (ver. 21.0, Inc., Chicago, IL, USA). Categorical variables were presented in number and percentage (%), and continuous variables were presented as mean ± standard deviation and range. Variables were compared using an independent t-test between the two groups. A P-value ≤0.05 was considered statistically significant.

RESULTS
Analysis of 40 patients with heel defect and their details were described (Table 2). There were 35 males and 5 females, with a male to female ratio of 7:1. The mean age of the study participants was 39.37 yr; ranging from 21 to 55 yr. The most common cause of heel defect was traumatic injury (21; 52.5%)  3. Severe difficulty on uneven terrain, stairs, inclines, ladders 0   Only two cases of medial plantar artery flaps, used after tumor excision, and two cases of the advancement of avulsed heel flaps used for posterior heel defects showed touch sensation at 10.75 months (11-12 months). Return of protective sensation and mean AOFAS subjective score was significantly higher in the nonneuropathic ulcer group (Table 4).

DISCUSSION
Reconstruction of Heel defect with durable tissue which can bear the load of daily activity and offers to bear of the normal shoe is the primary goal of surgery 7 . Based on the location of heel defects, it may be anterior, posterior, and complete. Isolated anterior heel defects at the weight-bearing part mostly occur as a consequence of neuropathies, tumor excision, and burn injury 7,9 . Longstanding anterior heel defects many times associated with osteomyelitis of calcaneum and foul-smelling discharge, which should be addressed during management. For the reconstruction of defects at the anterior weight-bearing part of the heel, the medial plantar artery, and local flaps are preferred because they have a thick epidermis and dermis which is similar to heel skin 4,7,10 . Use of local flaps like V-Y advancement, transposition, and rotation usually limited to cover small size anterior heel defects 9,18-20 . Medial plantar artery islanded flap best suited for moderate-sized anterior heel defects in terms of matching, durability, and cosmesis. If there is a trauma in the instep region or the course of the medial plantar artery, then other regional flaps like distally based fasciocutaneous flaps from the leg or free flaps can be used for reconstruction of the weight-bearing part of the heel. In our study, most of the anterior defects were neuropathic in origin and, the rest were posttumor excision and related to burn injuries. Smallsized anterior heel defects were covered with local suprafascial flaps like rotation, V-Y advancement flaps. Whenever possible, moderate-sized defects were covered with MPA islanded flaps based on the superficial branch of the medial plantar artery. In situations where the medial plantar artery flap was not possible, we performed an extended RSA flap along with the exteriorization of the fasciocutaneous pedicle to reconstruct anterior heel defects. Although it is a two-stage procedure main advantage over a single-stage sural flap is it maintains the contour of the uninvolved posterior heel and avoids unnecessary scar over the Achilles tendon region which may sometimes become painful while walking and also cosmetically not appealing ( Figure 3B) 14,21 .    Defects at the posterior non-weight bearing part of the heel which can occur due to prolonged immobilization or traumatic avulsion injury of the heel, it does not require coverage with thick glabrous plantar skin. Defects in this region are commonly associated with Calcaneum fracture or injury to the Achilles tendon region 7,8 . Skin grafting is indicated if the wound is superficial. In most of the studies Reverse sural artery and lateral calcaneal artery flaps are the commonly used procedure if the defect is deep with exposure of calcaneum or Achilles tendon [6][7][8]22 . We were able to close posterior heel defects due to avulsion injury by debridement and advancement of the avulsed heel flap. Posterior heel defects without avulsion component and posterior defects extending to the Achilles tendon region were covered by an islanded RSA flap. Posterior heel defects in this study were covered by conventional RSA flap because these defects were small in size as well as the distance between the defect and pivot point is not much, due to this skin paddle lies over the suprafascial course of the sural nerve and easily reach the site of the defect in a single stage.
For the reconstruction of a complete heel defect which involves both weight and non-weight-bearing part of the heel, local fasciocutaneous flaps are not adequate in size to cover the entire defect. Therefore, other options like reverse sural artery flap, distally based fasciocutaneous flap, free fasciocutaneous or muscle flap, cross-leg flap, and combination of two loco-regional flaps have to take into consideration. Large defects at the heel usually treated by free flaps but require expertise and infrastructure for microsurgery. Conventional RSA flap has a limited role in the reconstruction of large and distal foot defects, because of its described territory and unpredictable outcome [23][24][25] . Different modification of reverse sural flap-like flap delay, skin extension over pedicle, venous supercharging of the flap, etc. have been described to minimize the risk of venous congestion, flap necrosis and, also to expand the territory of the flap 14,25-31 . These modifications make the sural flap a reliable alternative to free tissue transfer in coverage of large foot defects and in patients with comorbidities it may be the preferred option.
We prefer extended RSA flap as a first choice to reconstruct complete heel defects because, it is an easy, safe, less time-consuming procedure and not requiring any additional microsurgical procedure.
An Extended RSA flap can be done single stage by splitting the intervening area lying between the pivot point and defect, or in two stages by exteriorization of the pedicle over the intervening area. The inclusion of skin over the pedicle has many advantages, as it provides additional blood supply as well as protect the pedicle from traction and twisting 14,27,28 . We did not encounter any venous congestion and major flap necrosis with this technique, even when the flap reaching up to the midsole region (Figure 4 A).
Although this technique requires second surgery for pedicle division, extra wound care at the pedicle site, and donor site morbidity at the calf region, but well accepted by the patients. In the two-stage flap technique, at the time of flap division and inset, the de-epithelized part of the pedicle can be utilized to fill the partial bony cavity in the case of calcaneal osteomyelitis (Figure 4 B). Other techniques described in the literature to fill the partial bony cavity with soft tissue after calcaneal debridement are musculocutaneous sural artery flap and combined muscle and skin flaps of the calf 32,33 . Our experience in free flaps is only with free LD muscle flap used in very large complete heel defects with bared bone. Cross leg flap should be discouraged because it gives a lot of discomfort to the patient, as it required long-standing immobilization in difficult positioning. We used cross-leg flap in the relative indication of heel reconstruction when other mentioned flaps option was not feasible. The drawback of the distally based flaps from the leg is; they are nonsensate and skin texture not similar to planter skin but in the long term, adaptive changes occur and protective sensation returns in the flap 6,10 . The advantage of the sensate free flap is an early return to daily living activity without the need for protective shoes 34 ; however, in the long run, patients with nonsensate free flap did not report difficulty in daily living activity compared with the sensate group. Santanelli et al 17 achieved most of the desired outcomes after flap surgery for the foot defects, like contour, stability, sensation, walking ability in a 1year postoperative follow-up period. In our study also most of the nonsensate flaps showed a return of protective sensation, which was higher in the nonneuropathic ulcer group 22/28 (78.5%) compared to the neuropathic ulcer group 4/13 (33.3%). The reason behind the return of protective sensation in the neuropathic ulcer group might be due to small anterior neuropathic heel ulcers with isolated www.wjps.ir Other studies, that used reverse sural flap for heel defects did not mention the recurrence of ulceration in their follow-up period 6,25,26,28,36 . No relevant differences was found in the functional results between different flap types and free or pedicled techniques used for reconstruction of the weight-bearing sole 4 . In our study mean AOFAS subjective score was highest for islanded RSA flap used in posterior traumatic defects (mean score of 54.66 of 60 points), followed by local flaps performed for small anterior and posterior defects with intact surrounding sensation (51.33 of 60 points). We found a lower mean AOFAS subjective score of MPA flap (40.5 of 60 points) compared to other studies 10 in which the score was 57.3 of 60 points. The reason behind, this low AOFAS score in MPA flap could be its use mostly in neuropathic ulcers.

CONCLUSION
For small defects, at the anterior or posterior heel region local rotation and advancement flaps are very useful without donor site morbidity. Medial plantar artery flap for moderate size anterior heel defects, extended reverse sural flap for complete heel defects, and islanded reverse sural artery flap for posterior heel defects can cover most of the Heel defect with a good durable cover and functional outcome. Return of protective sensation and functional outcome was significantly higher in the non-neuropathic ulcer group.

FINANCIAL SUPPORT
Nil.

CONFLICTS OF INTEREST
There are no conflicts of interest.